Federalism only works well when the States have the power to limit the central government.
Senators appointed by, and responsible to the State Governors and legislatures were the method our founders chose to do that.
The 17th amendment abolished that power of the states and established no replacement, and ever since the limited relatively weak Federal Government the founders envisioned has metastasized out of control.
So9
Legislative appointment of Senators was designed to minimize Democracy. State powers were deliberately reduced under the Constitution. The reason the Convention was called was specifically to increase the power of the National government and REDUCE the powers of the States.
Federalism is a structure wherein the States have NO power over National issues. Their powers are confined to affecting issues WITHIN the state boundaries and NOWHERE else.
Senators never represented state interests any more than Representatives did under the actual design of the constitution. Only by considering the State interest as viewed by the Legislature as somehow different than the State interest as viewed by the electorate could this method of appointment produce a divergent result from direct election.
An objective examination of the role of the Senate as stated in the Constitution clearly shows that it was concerned with the Long Term interests of the Nation. There is not one word in it pointing to a primary concern with state interests.